Add warnings about display:none and placeholder readiness to the README

git-svn-id: https://flot.googlecode.com/svn/trunk@66 1e0a6537-2640-0410-bfb7-f154510ff394

README.txt

@@ -21,7 +21,7 @@ you take the one bundled with Flot as it contains a bugfix for drawing
 filled shapes) which is canvas emulation on Internet Explorer. You can
 include the excanvas script like this:
 
-  <!--[if IE]><script language="javascript" type="text/javascript" src="excanvas.js"></script><![endif]-->
+  <!--[if IE]><script language="javascript" type="text/javascript" src="excanvas.pack.js"></script><![endif]-->
 
 If it's not working on your development IE 6.0, check that it has
 support for VML which excanvas is relying on. It appears that some
@@ -44,16 +44,24 @@ this:
 
    <div id="placeholder" style="width:600px;height:300px"></div>
 
-You can also do it with an external stylesheet.
+You can also do it with an external stylesheet. Make sure that the
+placeholder isn't within something with a display:none CSS property -
+in that case, Flot has trouble measuring label dimensions which
+results in garbled looks and might have trouble measuring the
+placeholder dimensions which is fatal (it'll throw an exception).
 
-Then on document ready, run the plot function:
+Then when the div is ready in the DOM, which is usually on document
+ready, run the plot function:
 
   $.plot($("#placeholder"), data, options);
 
 Here, data is an array of data series and options is an object with
 settings if you want to customize the plot. Take a look at the
 examples for some ideas of what to put in or look at the reference
-in the file "API.txt".
+in the file "API.txt". Here's a quick example that'll draw a line from
+(0, 0) to (1, 1):
+
+  $.plot($("#placeholder"), [ [[0, 0], [1, 1]] ], { yaxis: { max: 1 } });
 
 The plot function immediately draws the chart and then returns a Plot
 object with a couple of methods.